Find Out How Accurate Your Trendy Fitness Monitor Is

Activity monitors used to be tools that only scientists used during research, but the fitness-tracking industry, which is projected by analysts to be a $19 billion business by 2018. But how accurate are they really?

In a new study from Iowa State University published in the journal Medicine & Science In Sports and Exercise, researchers assessed how well they actually work. To test the products, 30 men and 30 women wore eight popular monitors during a 69-minute workout that included exercises like Wii tennis, running, and playing basketball. They also wore a medical-grade metabolic analyzer for comparison. The researchers found that some devices were pretty accurate, with estimates within 10 to 15% of precise calorie burn.

Here’s their list, ranked from most to least accurate:

1. BodyMedia FIT performed best with a 9.3% error rating. The researchers say this device has a similar accuracy to devices used in research. That’s probably because 10 years prior to releasing a consumer product, BodyMedia was developing products specifically for the medical research industry.

2. Fitbit Zip had a 10.1% error rating

3. Fitbit One had a 10.4% error rating

4. Jawbone Up had 12.2% error rating

5. Actigraph had a 12.6% error rating

6. Directlife had a 12.8% error rating

7. Nike Fuel Band had a 13% error rating

8. Basis Band had a 23.5% error rating

You can read more about the researchers’ work, here.